Fig. 1. Equipment diagram of the laser welding. (a) Physical picture; (b) schematic diagram

Fig. 2. Macro morphology, penetration depth and penetration width of the weld. (a) Heat input is 43.64 J/mm; (b) heat input is 46.16 J/mm; (c) heat input is 48.00 J/mm

Fig. 3. Effect of welding heat input on weld penetration depth and penetration width

Fig. 4. Macro morphology and microstructure of the weld. (a) Macroscopic morphology of the weld; (b) microstructure of the upper fusion zone of the weld; (c) microstructure of the lower fusion zone of the weld

Fig. 5. Effect of heat input on the grain size of the weld. (a) EQZ; (b) columnar crystal

Fig. 6. Microhardness of welded joints under different grain sizes

Fig. 7. Transverse tensile test result and fracture morphology of the T-joint. (a) Curve of the tensile force-displacement; (b)--(c) grain morphology of the fracture

Fig. 8. SEM image of the fracture surface of T-joint. (a)--(b) Heart input is 43.64 J/mm; (c) heat input is 46.16 J/mm; (d) heat input is 48.00 J/mm; (e) dimple morphology of the fracture surface; (f) morphology of the intergranular fracture